linux-kernel - Re: [PATCH 1/2] locking/rwsem: Add CONFIG_RWSEM_SPIN_ON

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Date:	Fri, 06 Jun 2014 11:12:38 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Jason Low <jason.low2@...com>
Cc:	peterz@...radead.org, mingo@...nel.org, mpatocka@...hat.com,
	torvalds@...ux-foundation.org, waiman.long@...com,
	jejb@...isc-linux.org, paulmck@...ux.vnet.ibm.com,
	dave.anglin@...l.net, aswin@...com, linux-kernel@...r.kernel.org,
	linux-parisc@...r.kernel.org
Subject: Re: [PATCH 1/2] locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER

On Fri, 2014-06-06 at 10:13 -0700, Jason Low wrote:
> On Fri, 2014-06-06 at 08:55 -0700, Davidlohr Bueso wrote:
> > Just like with mutexes (CONFIG_MUTEX_SPIN_ON_OWNER),
> > encapsulate the dependencies for rwsem optimistic spinning.
> > No logical changes here as it continues to depend on both
> > SMP and the XADD algorithm variant.
> > 
> > Signed-off-by: Davidlohr Bueso <davidlohr@...com>
> > ---
> >  include/linux/rwsem.h  | 4 ++--
> >  kernel/Kconfig.locks   | 4 ++++
> >  kernel/locking/rwsem.c | 2 +-
> >  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> Do we also want to add an #ifdef CONFIG_RWSEM_SPIN_ON_OWNER in
> __init_rwsem() and in the optimistic spinning functions for rwsem-xadd?
> 

Not really, as we conditionally build rwsem-xadd.o based on
CONFIG_RWSEM_XCHGADD_ALGORITHM:

obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem-xadd.o

So leaving just SMP is ok there.

> 
> Besides that:
> 
> Acked-by: Jason Low <jason.low2@...com>
> 

Thanks,
Davidlohr

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